It’s rare that home centers provide finishes with sheens other than gloss and satin (shellac comes in gloss only), but you can use these two to achieve any sheen you want.
Sheen is the amount of gloss, or reflection, in a finish. If no flatting agent is added – that is, there’s nothing at the bottom of the can that has to be stirred into suspension before application – the finish produces a gloss, or sharp image clarity. Manufacturers create satin and flat finishes by adding a flatting agent, which is usually silica. The more flatting agent added the less reflective the finish.
To get a sheen in between that of gloss and satin within any finish type – varnish, lacquer or water-base – simply mix the two (after stirring the satin, of course). To get a sheen flatter than the satin, let the flatting agent settle (don’t let the store clerk shake the can) and pour off some of the top. What is left will be much flatter. You can then mix these to get something in between if you want.
Because it is the top, or last, coat applied that is responsible for determining all of the sheen, you can change the appearance simply by applying another coat with a different sheen.
Spray guns can be used to produce nearly flawless, meaning almost perfectly level, surfaces. But you can achieve the same without a spray gun simply by thinning the finish or using an aerosol. The thinner (meaning “thinned”) the finish, the better it levels and the faster it dries.
Better leveling means no brush marks. Faster drying means reduced dust nibs.
You can thin any finish to get it to level better, but the easiest to use are the varnishes. All home centers carry already thinned alkyd and polyurethane varnishes. These are sometimes labeled “Wipe-On Poly,” but also “tung oil,” “tung oil finish” or “tung oil varnish.” In no cases do these products (which I call “wiping varnish” because they’re easy to wipe on wood) have anything to do with tung oil, but they produce wonderful results nevertheless.
There are three good ways to apply a wiping varnish: Wipe or brush it on the wood and wipe off all the excess; wipe or brush it on and wipe off some or most of the excess; brush it on and leave it. The more you leave the greater the build but the longer time dust has to settle and stick to the finish.
To get a thick build with fewer coats, brush several full-strength coats of alkyd or polyurethane varnish, sand the surface level up to #400-grit sandpaper, then apply several coats of wiping varnish and wipe off some or most of the excess. You can make the wiping varnish yourself by thinning the same finish you’re brushing by half with mineral spirits, or you can use one of the already thinned brands. (See “The Basics of Wiping Varnish” in the November 2005 issue, #151.)
You can also use an aerosol for your finishing. Aerosols are now available in oil-based polyurethane and water-based finish in addition to lacquer and shellac, but they are relatively expensive. Instead of building all your coats with the aerosol, you can brush a couple, sand out the brush marks then use the aerosol of the same type of finish to apply level final coats.
Whatever finish you’re applying and however you’re applying it, always watch it in a reflected light to spot runs as they develop and respread or rewipe to remove some of the excess.
Whatever method you use to get a level surface, rub it lightly with a folded brown paper bag after the finish has hardened to remove minor dust nibs and make the surface feel smoother.
Blotching is uneven, and usually ugly, coloration caused by stains penetrating the wood unevenly.
To avoid blotching on softwoods such as pine, use a gel stain. This is a stain thickened enough so it doesn’t penetrate. Gel stains ought to be called “pine stain” because they are so effective at eliminating blotching in pine.
On hardwoods such as cherry, birch, maple and poplar, it’s more effective to use a washcoat. This is any finish thinned to about a 10 percent solids content. Lacquer is used in industry, but the type sold in home centers is varnish or a blend of oil and vanish labeled “wood conditioner” or “stain controller.” You can make your own by thinning any full-strength varnish or blend of boiled linseed oil and varnish with two parts mineral spirits.
When you apply this washcoat, be sure to let it cure at least six hours in a warm room, better overnight, or it won’t be very effective. This is different than the directions on the cans, which usually say to apply the stain within two hours.
There is no need to apply a washcoat to woods such as oak, ash, walnut and mahogany that don’t blotch.
Colored glazes are used to add highlighting, antiquing or create faux graining over at least one coat of finish. Glazes are rarely available in home centers, but you can substitute a gel stain with excellent results. Glazes and gel stains are essentially the same thing anyway – a thickened stain.
To do glazing, brush or wipe the glaze or gel stain over at least one coat of finish and then remove all the color you don’t want using a rag, brush, sponge, graining tool (usually available at home centers), steel wool or any other tool that produces the results you want.
A typical use of glaze on cabinets and furniture is to leave it in recesses to add three-dimensional depth or an antique look. Be sure to apply at least one coat of finish over the glaze after it has dried to protect it from being scratched or rubbed off.
Some woods look better with their pores filled to create a “mirror-flat” surface. Mahogany is the best example.
Products called “paste wood filler” or “grain filler” (not the same as wood putty or wood filler) designed to achieve this look are rarely available at home centers. But you can achieve the same result by sanding a number of coats of finish down to the deepest level of the pores. You can sand a little between each coat, or you can sand more after you have applied all the coats.
Because we all apply finishes differently, you will have to experiment on scrap to determine the number of coats necessary so you don’t sand through.
For the easiest sanding between coats, use stearated sandpaper. Norton “3X” and 3M “Tri-Mite” and “Sandblaster” are all stearated. This means they contain a soap-like lubricant that reduces clogging. You can use your hand to back the sandpaper when sanding between coats, but you should use a flat sanding block on flat surfaces when sanding many coats level.
For the easiest sanding after a number of coats, use black, wet-dry sandpaper with a mineral-oil, mineral-spirits or mixed mineral-oil/mineral-spirits lubricant. Begin sanding with a grit sandpaper that levels efficiently without creating larger-than-necessary scratches (for example, #320 or #400 grit) and then sand to finer grits if they are available.
If finer grits aren’t available, apply one more coat of thinned finish (so it will level well), spray with an aerosol or rub the surface with #0000 steel wool. You can use a wax, oil or soap-and-water lubricant with the steel wool to reduce scratching and improve smoothness.
Problems in the Wood
Of all the finishes, shellac is easily the most effective for blocking off problems in the wood. The most common problem in new wood is resinous knots in pine and other softwoods. The resin can bleed into the finish and cause it to remain tacky and not cure.
In old (refinished) wood, the most common problems are fish eye (cratering or ridging) and odors from smoke or animal urine. Shellac blocks all these problems so you can then successfully apply any finish over it. If you are using varnish or water-based finish, it’s best if you use dewaxed shellac, sold in most home centers as “SealCoat.”
To make your own dewaxed shellac, pour off or decant the shellac from a can of Bull’s Eye Clear Shellac after the wax has settled to the bottom. It will take a long time for this to occur on its own, so don’t shake the can when you buy it, or thin the shellac with at least two parts denatured alcohol in a glass jar (so you can see it) to get it to settle faster.
If there are no problems you need to block off, there’s no reason to use shellac as a first coat.
Somehow, a lot of unnecessary mystique is introduced into wood finishing. In reality, however, it is quite simple. This is most evident when you realize all the possibilities available from just the few products stocked by home centers. PW